In recent years, engines, transmissions, brakes, steering or the like have been progressively controlled electronically in motor vehicles, and a cooperative control is performed by trans-communicating information between respective controllers through communication circuits.
However, with the motor vehicle installed with such electronic control units, there is a possibility that the entire electronic control units become non-operatable when a failure of the main battery is caused at the time of an accident of the vehicle or the like.
An emergency notifying system which is installed on a vehicle that changes over a supply of electrical power to an auxiliary battery when the main battery is failed at the time of an accident or the like is disclosed in JP2000-278885.